Electrical codes generally require that wire or cable entering junction boxes be clamped and thus immobilized to prevent connections from loosening and accidentally causing a disconnect. Clamping also prevents insulation jackets from being chafed by moving contact with exposed portions of the junction box, and thereby reduces the risk of electrical short circuits and associated damage.
This invention is primarily concerned with connections to standard electrical junction boxes for nominally 110–220 volt, alternating current electrical service in residential, commercial and light industrial electric power supply service. Outdoor, weather-exposed junction boxes typically have one or more connector receptacles formed by a built-up boss in the box wall. The boss is usually drilled and female screw threads are formed on the interior surface of the resulting hole through the boss. These threads are designed to mate with male threads of a connector. After threading the connector into the receptacle, wire can be inserted axially through and clamped to the connector. Vacant receptacles are sealed with screw caps. For indoor applications where the box is sheltered from weather conditions, the junction boxes typically have a thin wall construction, usually of metal or plastic. The wall of this type box normally has one or more knock-out style connector receptacles which basically includes a pre-cut, typically circular hole with a cover. The cover is of the same material as the wall of the box and is usually completely separated from the perimeter of the hole except for a small link. When a particular connector receptacle is to be used, the cover is pried away from the wall which causes the link to flex and break. This exposes a hole of suitable size that a male-threaded end of a connector can be freely inserted and secured with a female-threaded, typically thin, ring-shaped nut.
Among many types of electrical connectors for junction boxes two in common use are of interest with respect to the present invention. The first, and perhaps older, is a typically metallic, generally tubular structure, male threaded device, sometimes known as a “Romex” connector. It has male threads at one end and a vise-style cable clamp at the other end. The cable clamp uses specially formed vise jaws adapted to squeeze together and thereby seize a cable inserted between the jaws when clamping screws that are provided as part of the clamp are turned. Generally a screwdriver or similar tool is required to tighten the clamping screws.
These clamp connectors are designed for use with either the outdoor (i.e., threaded) or indoor (i.e., knock-out style) junction box connector receptacles. For a threaded receptacle, the male threaded end of the connector is screwed directly into the receptacle. For knock-out style receptacles, the threaded end of the connector is passed through the hole and a female threaded lock nut is screwed onto the male threads from the other side of the box wall. The sizes of the connector body and the lock nut are selected to anchor the connector against the wall.
This type of connector has notable shortcomings. First, it is time-consuming and labor intensive to install. This is because the connector must be mounted on the box either by threading into a receptacle or by screwing on a lock nut and then the clamping screws must be tightened to clamp the cable between the vise jaws. Second, the clamping of the jaws can be difficult due to placement of the box in relation to the structure being wired. That is, the clamping screws may be awkward or essentially impossible to access for tightening after the box is assembled, installed and the cable is inserted through the connector. Thirdly, because it is made of metal and the jaws can be tightened too much, the clamp can penetrate the cable jacket and short circuit the conductors. Fourthly, the vise-jaw portion of the connector usually extends at least about ½ inch outside the box. When a box is mounted near a flat structure finished wall, the connector often contacts the wall and causes the box to pivot (i.e., to rock) about the point of contact rather than lie flat against the wall. This is unsightly and can lead to wear and deterioration of the structure finished wall.
The second, perhaps more recently developed conventional connector, sometimes known as a “Hit-lock” overcomes some of the above-mentioned shortcomings. This clamp connector is typically made of plastic and is designed to snap into the unthreaded holes of a junction box knock-out style receptacle. It has a generally cylindrical structure with a broad flange at one end and a secondary flange stubs protruding radially outward a short distance from the broad flange. The connector is snapped into the receptacle usually by tapping the broad flange face with a hammer such that the stubs are forced through the receptacle hole and, together with the interior face of the broad flange, grip the wall of the box to mount the connector in place. The cable is held in place by a jamming clamp having several prongs pointing toward the inside of the connector. The cable is pushed into the junction box through the connector between the prongs. The prongs bear upon and bite into, but do not penetrate, the cable jacket, thereby preventing the cable from being pulled in the opposite direction out of the box.
While the “Hit-lock” connectors are non-conductive and do not have vise-jaw style, screw-threaded clamps, they do not overcome all of the above listed disadvantages of the “Romex” connectors. Most notably, they are designed for use only on unthreaded holes. There thus is a need and an opportunity in the electrical arts for a connector device that is non-metallic, avoids a “screw down” cable clamp, and which can be used in a threaded receptacle outdoor junction box. There is also a desire to have a single cable connector that can be used with both indoor and outdoor style junction box receptacles. There is further need for a connector that allows a junction box to mount closely and securely to a structure finish wall.